Japanese Housewarming Celebration
When a couple gets married, and buys a new house, they have a big dinner for a housewarming celebration. At this dinner, everyone is supposed to eat fish eggs, usually eaten with rice.
The informant claims that eating the fish eggs is supposed to bring good luck, especially in the realm of starting a family. This practice is supposed to help them have a baby, hence the connection of eggs with fertility.
I agree with my informant. Because the new couple has a new house, I suppose it would be expected to fill that house with a family, including children. Id also like to add that I think this celebration involves fish eggs rather than another kind of egg because fish are an important staple of a traditional Japanese diet, as Japan is an island surrounded by water.